Is 40Gbit/s Sonet/SDH back?

Is 40Gbit/s Sonet/SDH back?
It was a huge hype in the end of the 90s, but the telecom bubble closed such efforts down. With fiber glut and capex cuts, no way to deploy such new systems. For a while, this segment market seemed forgotten by vendors, operators and chip makers. And step by step, talk of a 40-Gbit/s revival started simmering, first in dedicated conferences, then chip makers and vendors. Pioneers are always MCI/ Verizon, Siemens, Alcatel and Lucent and a lot of small start-ups, such as Kailight Photonics, StrataLight, CoreOptics, etc. The technology has evolved also with the use of optical duo-binary signaling (ODB), or return-to-zero differential phase-shift keying (RZDPSK). By 2H06, some ODB-based transponders would be sampled, and it will be necessary to wait until the end of the year to have RZDPSK-based transponders for qualification.

But demand is not yet there (except some particular needs), and the market should be still small for a while.